Embodiments of the present invention generally relate to a system and method for performing a hearing screening, and more particularly, to a system and method for performing a hearing screening using a plurality of audiometric evaluations and measurements.
Typical audiometric evaluations and hearing screenings include several measurements used either in isolation or in combination. The measurements include acoustic measures, such as tympanometry and acoustic reflexes; evoked responses, such as otoacoustic emission measures and auditory brainstem response; and behavioral responses, such as pure-tone testing.
With respect to tympanometry, a probe having an eartip is placed in the opening of the ear canal. The eartip sealingly engages the opening of the ear canal. A probe tone (for example, 226 Hz or 1 kHz) is transmitted within the ear canal, while the air pressure in the ear canal is varied from positive to negative within a specified range (for example, +200 to −400 daPa). Reflected sound from the tympanic membrane is used to determine the middle ear pressure, that is, peak compliance, and mobility of the system, that is, static compliance. The peak compliance and static compliance reflect the status and function of the tympanic membrane, ossicles, middle ear space and Eustachian tube, thereby providing an objective measure of the auditory periphery to the point of the middle ear.
As noted above, tympanometry utilizes pressure fluctuations within the ear canal. Typical tympanometry devices include a continuous pump used to produce pressure differentials within the sealed ear canal (that is, the eartip of the probe sealingly engages the opening of the ear canal). Continuous pumps, however, may produce pressures that may damage anatomical structures within the ear. In short, the continuous pumps do not have limit stops or other features that limit levels of imparted pressure. For example, a continuous pump may be continually operated to produce a positive pressure. If left unchecked, however, the resulting pressure may exceed the threshold of pain for a particular individual. In short, there is no inherent limit to the amount of pressure that may be generated with respect to tympanometry systems that include continuous pumps. Also, typical tympanometry systems are large and bulky due, in part, to the continuous pumps contained therein. For example, the continuous pumps typically include large motors connected to a peristaltic pump, thereby adding size and bulk to the tympanometry system.
Otoacoustic emissions (OAEs) represent another hearing test, and are a direct measure of cochlear status as represented by outer hair cell function. The cochlea is the sensory organ of hearing responsible for transmitting acoustic information to the auditory nerve. The outer hair cells of the cochlea play a critical role with respect to processes within the cochlea. In a normal cochlea, the outer hair cells are involved in an active process known as the cochlear amplifier. As a byproduct of their active processes, the outer hair cells produce a low level sound that may be measured in the ear canal with a sensitive low-noise microphone. The low level sound is known as the otoacoustic emission. In the presence of sensory hearing loss, an otoacoustic emission is absent or significantly reduced in amplitude. Otoacoustic emissions are classified by the type of stimulus used to evoke the response from the outer hair cells. Transient evoked otoacoustic emissions (TEOAEs) are emitted in response to a short duration stimulus such as a click. Distortion product otoacoustic emissions (DPOAEs) are emitted in response to a simultaneous presentation of two pure tones of differing frequencies. TEOAEs and DPOAEs represent the two most common types of clinical otoacoustic emission measurements. Otoacoustic emission measurements are used to assess the function of the auditory periphery to the point of the cochlea, specifically the outer hair cells of the cochlea.
Acoustic reflex (AR) is a measurement of the contraction of the stapedius muscle in response to a high intensity stimulus. In acoustic reflex testing, air pressure within the ear canal is maintained at the point of peak compliance while tones of various intensities and/or frequencies are presented. Contraction of the stapedius muscle in response to a loud sound stiffens the conductive mechanism, causing a change in middle ear immittance, which may be detected. The acoustic reflex arc involves the cochlea, cranial nerve VIII (auditory nerve), ventral cochlear nucleus, superior olivary complex, facial nerve nucleus, cranial nerve VII (facial nerve), and the stapedius muscle. As such, an acoustic reflex measure is used to assess auditory pathways to the point of the superior olivary complex of the brainstem.
Auditory brainstem response (ABR) is an evoked potential in response to a brief click or tone-burst stimulus delivered to the ear via an earphone. The response waveform is measured with electrodes placed on the scalp and earlobes. Evaluation of the resulting waveform provides an assessment of the auditory system to the point of the inferior colliculus of the brainstem (one level above the superior olivary complex).
A strong commitment to the prevention, early detection and treatment of hearing loss and otologic disorders exists within the audiology, education, and medical communities. To that end, screening measures are used to identify those individuals who may, upon complete evaluation, demonstrate a hearing loss or pathology requiring remediation or medical treatment. The emphasis on early detection of hearing loss stems from the desire to begin audiological and/or medical intervention as soon as possible. The presence of childhood hearing loss is known to interfere with the development of speech and language skills. According to the American Speech-Language-Hearing Association (ASHA), “Hearing impairment adversely affects the developing auditory nervous system and can have harmful effects on social, emotional, cognitive, and academic development, and, subsequently, on the individual's vocational and economic potential.” See American Speech Language Hearing Association Audiologic Assessment Panel 1996, Guidelines For Audiologic Screening (1997). The probability of preventing permanent development delays increases the earlier a hearing impairment is identified and treatment begins. See id. It is with this knowledge that ASHA audiologic screening guidelines recommend regular screening for hearing disorder and hearing impairment for children age birth to eighteen years. See id.
Available screening procedures include otoscopic evaluation, tympanometry, otoacoustic emission (OAE) measurements, auditory brainstem response (ABR), and pure-tone testing. Each of these measures assesses the auditory system to a certain anatomical point. Otoscopy allows for visual evaluation of the external ear canal and tympanic membrane. Tympanometry assesses the function of the middle ear system (tympanic membrane and ossicles). OAEs are a direct and objective measure of the outer hair cells of the cochlea (sensory) and the ABR assesses the auditory system to the point of the brainstem (neural). Finally, in pure-tone testing a tone is delivered to the patient and a response is required from the patient thereby evaluating the auditory system to a cortical level. OAE testing is the newest measurement type of those described, having entered the clinical arena in the early 1990's. In the last decade, OAEs have gained nearly unanimous acceptance as a means of screening for sensory hearing loss, the most common type of permanent hearing loss. OAEs are particularly useful for screening newborns, infants, and children as no response is required from the patient. As part of the diagnostic audiology test battery, OAE measurements are conducted on patients of all ages.
According to ASHA screening guidelines, “Ideally a screening test should be easy to administer, comfortable for the patient, short in duration, and inexpensive.” See American Speech Language Hearing Association Audiologic Assessment Panel 1996, Guidelines For Audiologic Screening (1997). An objective measure is particularly desirable when testing young children or other difficult-to-test populations and when the tester has no particular education and/or expertise related to audiometric evaluations. Additionally, the test should be able to separate those with hearing loss from those without hearing loss via a “pass” or “refer” outcome. No test can offer 100% specificity and sensitivity but it is important to avoid a high over-referral rate due to the burden it places on follow-up resources. On the other hand, a high under-referral rate must also be avoided. Failure to identify individuals with hearing loss results in delayed treatment and ultimately a loss of faith in the screening program.
Often, emphasis is placed on identifying only sensory or neural hearing losses. This focus is most likely due to the often severe and permanent nature of sensory-neural hearing loss. Equally important, however, is the ability to detect middle ear pathology such as chronic otitis media with effusion and related conductive hearing loss. Within the pediatric population there is a high prevalence of middle ear pathology that is known to have both medical and developmental consequences. See, e.g., American Speech Language Hearing Association Audiologic Assessment Panel 1996, Guidelines For Audiologic Screening (1997), and, “Classroom Management Of Children With Minimal Hearing Loss,” Flexer, C., Hearing Journal, Volume 48(9), pp. 54-58 (1995).
In screening for sensory hearing losses in the school-age population, testing is commonly conducted with OAE or pure-tone testing. The decision to use one method over another will depend on the age of the patient, assessment of risk factors and patient history, skill level and training of the tester, available equipment, protocol of the screening program and a myriad of other factors. There are advantages, disadvantages and limitations to each type of test. In screening for middle ear pathology, some authorities support the use of tympanometry combined with a second measure such as pure-tone or OAE testing. See, e.g., “Outcomes Of Transient Evoked Otoacoustic Emission Testing In 6-Year Old School Children: A Comparison With Pure Tone Screening And Tympanometry,” Driscoll, C., Kei, J., & McPherson, B. Int. J. Pediatr. Otorhinolaryngol, Volume 57(1), pp. 67-76 (2001); “Distortion Product Otoacoustic Emissions In Children At School Entry: A Comparison With Pure-Tone Screening And Tympanometry Results,” Lyons, A., Kei, J., & Driscoll, C., J. Am. Acad. Of Audiology, Volume 15(10), pp. 702-15 (2004); and “Screening For Hearing Loss And Middle-Ear Disorders In Children Using TEOAEs,” Taylor, C., & Brooks R., American Journal Of Audiology, Volume 9(1), pp. 50-55 (2000). Therefore, if detection of middle ear pathology is included as an objective of the screening program, the protocol will likely include tympanometry.
As noted above, an effective screening program should aim for low rate of over-referrals (that is, false-positives) and under-referrals (that is, false-negatives or misses). While some authorities support the replacement of pure-tone screening with OAE testing based on sensitivity and specificity data, neither OAE nor pure-tone testing is a suitable replacement for tympanometry. See, e.g., “Outcomes Of Transient Evoked Otoacoustic Emission Testing In 6-Year Old School Children: A Comparison With Pure Tone Screening And Tympanometry,” Driscoll, C., Kei, J., & McPherson, B. Int. J. Pediatr. Otorhinolaryngol, Volume 57(1), pp. 67-76 (2001); and “Screening For Hearing Loss And Middle-Ear Disorders In Children Using TEOAEs,” Taylor, C., & Brooks R., American Journal Of Audiology, Volume 9(1), pp. 50-55 (2000). Additionally, OAEs typically provide a much shorter test time, as compared to pure-tone testing, particularly with respect to the younger range of the pediatric population.
In any event, in order to perform various screening tests, various testing systems are used. For example, if OAE testing and tympanometry testing are to be performed, a screener typically uses an OAE system and a separate and distinct tympanometry system that may be large and bulky. The screening process using these tests takes time because the screener typically changes screening hardware between tests. For example, the OAE system includes its own probe, while the tympanometry system includes a separate and distinct probe. As such, the screener must switch probes between tests.
Thus, a need exists for a safe, compact system and method for performing OAE and tympanometry screening. Additionally, a need exists for quickly and effectively performing a variety of hearing tests.